Michael Moore's Stupid White Men makes a brave and impressive showing at number seven, but otherwise the literary profile seems to mirror the country's political course. With Republicans in control of the White House and both Houses of Congress, America appears to be in a belligerent, rightwing mood. And while most of the world might complain about the Bush administration or, at most, seek to contain its excesses, only Americans can get rid of it.

Which raises the question: whatever happened to the left in America? What became of the political culture that stopped the Vietnam war, brought about civil rights and very nearly made Jesse Jackson the Democratic presidential candidate? Where are the popular, progressive forces that could challenge the Bush administration from within? Ask leftwingers this - people who have devoted their life to progressive causes - and most of them will laugh. "The left is not a word you mention in polite company here," says Karen Rothmeyer, an editor on the leftwing weekly, the Nation. "We talk about the right, but we never talk about the left."

The difference is more than linguistic. While the left in Europe does not represent a fixed point - Roy Hattersley, for example, finds himself on the left now, but he didn't 15 years ago - it is more or less a known quantity. The assortment of social democrats, greens, trade unionists, communists and Trotskyists share a tradition and broad aims, even if they often spend more time arguing with each other than the right.

"The concept 'American left' is subject to quite a range of interpretations," says Noam Chomsky. "Take the solidarity movements in the 80s, which broke new ground in the history of European imperialism, when thousands of Americans not only protested but went to live with the victims of the US terrorist wars, both to help and to offer some protection against the terrorist forces run from Washington. Was that 'left'? The roots were mostly Main Street, Iowa.

"Today I spoke to a group of union organisers and leaders. Are they 'left'? They certainly are open to a far-reaching critique of state capitalist institutions, though I suppose a lot of them are 'Reagan Democrats'. It's a complicated country."

Just how different America can be was evident from the placards at the most recent anti-war demonstration. Compared with similar British marches, it was more religious - "God loves people against the war", "Peace is Jewish" - and, more patriotic - "Love my country, hate my government", "Peace is the American Way". It was also far less union-oriented - there were very few banners from trade unions - and without any discernible input from mainstream politics.

"Democrats are subject to the same thing Republicans are - big money," says Katha Pollitt, a columnist for the Nation. "What we think of as the left is really a collection of single or dual issues that network with each other but there really isn't a home for them. There are people doing good work in their community but they're not really hooking into the electoral process."

There are the students against sweatshops, the environmentalists, feminists, anti-racists, union organisers and pacifists: the collection of groups that have found themselves incredibly effective beyond their own field on the few occasions when they have been able to work together, as in Seattle a few years ago.

But whatever you want to call it, and wherever its home is, contrary to popular belief on both sides of the Atlantic, the American left does exist. True, there were few people flocking to the banner calling on people to "Break with Democrats [and] Build a workers' party to fight for socialist revolution" at the anti-war demonstration in Washington earlier in January. But there were several thousand others marching with placards saying everything from "Drop Bush not Bombs" to "Regime change starts at home".

On their own they would have reflected little more than a sizeable but, none the less, unrepresentative and discontented rump. Dominant among the march organisers, although not the demonstrators themselves, were members of Workers World, a Marxist group which, among other things, has expressed support for Slobodan Milosevic and the regimes in Iraq and North Korea. Key figures in the Not in Our Name statement condemning war, which has attracted thousands of signatures, including those of Susan Sarandon, Gloria Steinem, Gore Vidal, Alice Walker and Kurt Vonnegut, are members of the Revolutionary Communist party. The New York Daily News mocked them as "a coalition of superannuated Maoists, anarchists, Saddamites, Starbucks-resisters and anti-imperialists".

But all the evidence suggests that while the left may be small and elements of its leadership may be extreme, its general message is beginning to resonate well beyond its own borders. "The left is never popular as such, but the issues it raises can be popular," argues activist and historian, Howard Zinn. This has been most striking in recent times on attitudes towards the war. "What was really encouraging about these last demonstrations wasn't just their size but who was on them," says Pollitt. "They came from a very broad section of the country. There were lots of homemade signs and people from as far away as Fargo, North Dakota."

All the polls suggest a steady increase in opposition to war if the US acts without UN approval, and support for giving the weapons inspectors more time. A Republican business group recently paid for a full-page advertisement in the Wall Street Journal, warning Bush: "The world wants Saddam Hussein disarmed. But you must find a better way to do it." Seventy-two city councils, including Philadelphia, Austin, Chicago, Baltimore and Cleveland have passed anti-war resolutions. And while comparisons with Vietnam remain valid, they must also be contextualised. "Some of us were in the street about the Vietnam war in 1961," says Grace Paley, one of the founders of the Green wich Village Peace Centre in 1961. "But there were no big demonstrations for four years. This is moving much faster, but so is Bush."

Chomsky agrees. "Today, in dramatic contrast to the 60s, there is large-scale, committed and principled popular protest all over the US before the war has been officially launched," he says. "That reflects a steady increase over these years in unwillingness to tolerate aggression and atrocities."

And while this has been most striking over issues relating to the war, it is being seen in other issues, too. Membership of the country's best known civil liberties advocates, the American Civil Liberties Unions, has surged 20% since September 11. Membership of the environmentalist group, the Sierra Club, has risen by 16% since 2000, primarily in response to the threat Bush poses to the environment, a spokesman suggested. Bush's approval ratings are coming down to where they were when he first took over. "On nearly all the key issues - health care, education, social security - the Democrats still have an advantage," says Carroll Doherty, the editorial director of the non-partisan polling institute, the Pew Research Centre. "In a completely ambiguous way, the left represents American values right now," says Jennifer Baumgardner, a writer and activist.

Anecdotal evidence suggests this is more than just wishful thinking. In Peoria, Illinois, long a signifier for the mood of Middle America in much the same way as the man on the Clapham omnibus was in England, the local newspaper's website has run more letters that are sceptical about the war than in favour of it. "We all know that Saddam is scum and causes much suffering. He's less of a danger right now than is the United States. Define terrorism," writes Paul Snodgrass in one of them. Following a lecture tour to promote his book last summer, Michael Moore said he felt he was addressing mainstream America. "I look out at the auditorium or gymnasium and I don't see the tree-huggers and the granola-heads. I see Mr and Mrs Middle America who voted for George W Bush, who just lost $60,000 because their 401(k) [private retirement plan] is gone," he said. "They believed in the American Dream as it was designed by the Bushes and Wall Street, and they woke up to realise that it was just that, a dream."

On Flatbush and Seventh Avenue in Brooklyn on a cold week night, Jay holds up his handmade poster, declaring: "Bush is Lying." There are around 10 people at this anti-war vigil, carrying billboards and posters. Cars occasionally hoot in support. Jay says he has had no abuse. "If you're doing an article about the left in America, you'd better hurry up before we're all gone," he jokes. But across town, at the city technology college, around 200 activists have gathered on the same night to protest against plans to close token booths in subway stations and put up fares by 50 cents. If anything, the focus for many Americans at this time of international turmoil is more local than ever. Individual states, which have to run balanced budgets, are facing the most severe fiscal crisis since the war and are either hiking taxes, cutting services or increasing prices, and often a mixture of all three.

And while people are angry, the Democrats have not emerged as a natural beneficiary of their frustration. Despite war doubts and rising unemployment, Bush remains popular. More than half approve of his work in the past few weeks, 76% regard him as a strong and decisive leader, and 83% believe he is ready to make hard decisions. "People who disapprove of him on the economy still admire him personally," explains Doherty. And if support for the war is soft, then opposition to it is no less so. Slightly more than half (52%) say they would still support US military action, even if the weapons inspectors do not find evidence that Iraq has chemical, biological or nuclear weapons.

This mood, of course, has a lot to do with September 11 which, much more than in Britain, made an already hostile political landscape virtually uninhabitable for the left. When Susan Sontag suggested that "cowardly" was not an appropriate word to describe the perpetrators of the World Trade Centre attack, there were calls for her to be stripped of her citizenship. On September 12 Alan Madison, of the Sierra Club sent a memo to its local organisations asking them to hold off on demonstrations and advertising. "In those days you had to resonate with the population. You had to communicate in a way that would be in keeping with the times. No one was thinking about environmental issues at that time," he said.

"There was this sense that a lot of things can't be said that should be said. It was terrible," says Pollitt. "Flag-waving became the secular religion. Even Dissent magazine was asking whether there is any such thing as 'a decent left'. Patriotism is always available to attack the left about."

Complaints that the media was, at worst, openly partisan in favour of Bush and, at best, cowed into withholding criticism against his administration - and therefore refused to cover demonstrations and other leftwing activities - are too widespread just to be dismissed as the sour grapes of conspiracy theorists. One of the nation's most respected television anchormen, Dan Rather, said that the patriotic fervour that swept the country after September 11 prevented the media asking difficult questions. "It is an obscene comparison ... but you know there was a time in South Africa that people would put flaming tyres around people's necks if they dissented," said Rather. "And in some ways the fear is that you will be necklaced here, you will have a flaming tyre of lack of patriotism put around your neck."

But as time goes on it becomes increasingly untenable to pin the left's relative weaknesses on September 11. Not because it does not remain a factor, but because for any political force to remain relevant it must adapt to the situations it finds itself in any given time. "The terrorism agenda does affect things," says Doherty. "But increasingly it is not dominating the overall agenda."

In any case, the left's problems did not start on September 11. Half a century after McCarthyism, it is still struggling to gain a foothold in mainstream political culture. "It wasn't that big on September 10," says Pollitt, who believes a shift to the left in America would demand a fundamental shift in the way American politics operates. "Moving to the left would demand more than what politics is about in this country, which is putting campaign ads on television."

Bush's victory in November 2000 had left many demoralised, says Zinn. "Certainly, a lethargy had set in ... a hollowing out of enthusiasm and accusations that [Ralph] Nader was responsible for the election of Bush," he says. Rows over the extent green candidate Nader's decision to stand in such a close race handed victory to Bush will, it seems, continue to obsess the left long after the hanging chads of Florida are forgotten.

On a cold night in Times Square, the Missile Dick Chicks - a political satire on the chart-topping, all-American Dixie Chicks, who sang the national anthem at the Super Bowl last month - are well into their routine. Three women, each with a red, white and blue wig and model missiles strapped to their waists like vibrators, are singing, to the tune of the Supreme's Stop in the Name of Love: "Shop, in the name of war/ You need a whole lot more/ Don't think it over." A mostly bewildered audience includes a sprinkling of appreciative voices for their innovative protest. Behind them, a neon ticker tape quotes Powell saying the US will work with the UN if it can act with "a coalition of the willing" if it has to, and that the Dow has fallen again.

While the left has managed to slow down the right, it is a long way from being in a position where it can set the agenda.

"The Democratic party has no foreign policy," commentator George Packer wrote in the latest edition of the leftwing magazine, Mother Jones. "It hasn't since Vietnam. Their failure to stand up to the Bush juggernaut is more symptom than cause. They can't stand up because they have nowhere to stand, no alternate vision of what purpose America's enormous power in the world should serve."

Earlier this month it emerged that Democrats were so desperate to popularise their message that they formed a group, Democracy Radio Inc, overseen by a former Democratic Congressional staffer, Tom Athens, to go on the lookout for liberal populists to take on the rightwing shockjocks and Fox channel presenters who dominate the airwaves.

"We're going to go out and identify talent and help them to create programming and actually connect them with local stations," Athens said. "We want to plant a thousand seeds and see how many flowers actually arise."

Few held out much hope. "Most liberal talk shows are so, you know, milquetoast, who would want to listen to them?" said Harry Thomason, the Hollywood producer who is close to Bill Clinton. "Conservatives are all fire and brimstone."

The large number of Democrats who have declared themselves for the presidency suggests that Bush remains vulnerable. But few inspire great enthusiasm, either because they have no chance or because it is felt they will make little difference.

It is a testament to the left's strength that from the bleakest of scenarios they have created a space within which they are not just existing, but expanding. It is a sign of their weakness that they are expanding from such a small base that they are able to influence public opinion but not lead it. "There is an opening, but it's going to need some ideas to take advantage of it," says Doherty. "That's the big piece of the puzzle."

"The left is not a word that you mention in polite company here" Karen Rothmeyer, editor of the Nation

"The Democratic party has had no foreign policy since Vietnam. Their failure to stand up to the Bush juggernaut is because they have nowhere to stand" George Packer, writer

"Today I spoke to a group of union organisers. I suppose a lot of them are 'Reagan Democrats'. Are they 'left'?" Noam Chomsky

"If you're doing an article about the left in America, you'd better hurry up before we're all gone" Jay, anti-war protester

"After September 11, even Dissent magazine was asking whether there was such a thing as 'a decent left'" Katha Pollitt

The following correction was printed in the Guardian's Corrections and Clarifications column, February 14 2003

We said "Key figures in the Not in Our Name statement condemning war, which has attracted thousands of signatures, including those of Susan Sarandon, Gloria Steinem, Gore Vidal, Alice Walker and Kurt Vonnegut, are members of the Revolutionary Communist party." To be absolutely clear: we meant to say that key figures involved in drafting the statement are in the Revolutionary Communist party. That does not mean that those who signed are members of the party or support its views or policies.